THE PETROLEUM GEOLOGICAL CONDITION AND EXPLORATION PROSPECT ANALYSIS IN SINIAN,SICHUAN BASIN

The exploration degree of Sinian in the Sichuan Basin is low according to drilled information analysis.The drilled wells distribute on Leshan-Longnüsi paleo-uplift area and orogenic belt which is around the basin,but they almost failed.The source rock and caprock are good and have good geological conditions to form large gas field.The first oil generation period was in Caledonian and the oil was destroyed to bitumen in Hercynian.The second oil generation was in Indosinian.The Leshan-Longnvsi paleo-uplift was important to oil accumulation in this period.The oil was thermal cracked to gas by deep buried before Himalayan.It also formed abnormal high pressure and induced gas dissolving into water.During the uplift processes,due to the redistribution of gas and gas released from formation water,the gas field and gas-bearing areas were finally formed.Through analyzing the reservoir forming conditions of Sinian in the Sichuan Basin,this paper points out that the paleo-structures before Himalayan and Tianjingshan paleo-uplift in Caledonian should be the favorable exploration areas in the future.